JP2007238805A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition having improved reinforcing property and abrasion resistance. <P>SOLUTION: This rubber composition comprising (a) a dienic rubber, (b) silica, and (c) a sulfur-containing silane coupling agent is characterized in that, before the dienic rubber, the silica, and the a sulfur-containing silane coupling agent are kneaded, the dienic rubber is preliminarily kneaded with (d) disodium hexamethylene-1,6-bis(thiosulfate) dihydrate represented by formula : NaO<SB>3</SB>S-S-(CH<SB>2</SB>)<SB>6</SB>-S-SO<SB>3</SB>Na 2H<SB>2</SB>O at a temperature of 100 to 140°C in an amount of 0.1 to 10 pts.wt. per 100 pts.wt. of the dienic rubber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition having improved reinforcement and wear resistance.

  Conventionally, carbon black having high reinforcement and wear resistance has been used as a reinforcing filler for rubber. However, in recent years, there has been a social demand for energy saving, resource saving, environmental problems, etc. In order to save consumption, it is known to add silica, and the addition of silica to the rubber composition provides the advantage of improving wet performance in addition to reducing rolling resistance. However, since silica has a low affinity for rubber molecules, it is inferior in terms of reinforcement and wear resistance compared to carbon black. Therefore, in order to improve the dispersibility and workability of silica for the purpose of obtaining high reinforcement and wear resistance such as carbon black, rubber compositions containing silica are generally used in silane coupling. Agents are used in combination. However, when silica and carbon are simply mixed at the same time, the carbon and rubber are sufficiently contacted and reacted to promote sufficient mixing, but the silica is not sufficient, causing poor silica dispersion and sufficient silica characteristics. It was not alive. Various proposals have heretofore been made to solve this problem, but none of them are satisfactory in practice.

In order to increase the processing speed of the diene rubber composition, it has been proposed to add sodium thiosulfate (Patent Document 1), and in order to improve the heat aging resistance and adhesiveness of the rubber, reinforcement filling In the rubber composition containing carbon black as an agent, the following formula:
NaO ₃ S—S— (CH ₂ ) ₆ —S—SO ₃ Na.2H ₂ O
It is proposed to blend hexamethylene-1,6-bis (thiosulfate) disodium dihydrate (hereinafter referred to as “HTS”) represented by (Patent Document 2), but a reinforcing filler Dispersibility of silica added after blending HTS by blending HTS uniformly into rubber component before blending silica and silane coupling agent into rubber component when blending a rubber composition containing silica as It has not been proposed so far to improve the reinforcement and wear resistance of the resulting vulcanized rubber composition.

JP-A-9-118784 Japanese Patent Laid-Open No. 10-195237

  The problem to be solved by the present invention is to provide a silica-containing rubber composition in which the dispersibility of silica is enhanced in view of the above-mentioned drawbacks of the prior art, thereby improving the reinforcement and wear resistance.

The present inventor paid attention to the reactivity of HTS, that is, the reactivity that HTS is thermally decomposed at about 120 ° C. to release bound water, and in the production of the silica-containing rubber composition, the diene rubber is combined with silica. Before compounding the silane coupling agent, HTS was previously kneaded with diene rubber at a predetermined temperature to decompose the HTS, thereby improving the dispersibility of the silica, resulting in improved reinforcement and wear resistance. The inventors have found that a silica-containing rubber composition can be obtained, and have completed the present invention. Before blending silica and a silane coupling agent into diene rubber, HTS and diene rubber are kneaded at a temperature of 100 to 140 ° C. (hereinafter, this kneaded material is referred to as a first kneaded material). The water released by the decomposition of HTS (hereinafter referred to as “water derived from HTS”) is present in a substantially uniformly dispersed state in the first kneaded product, and then silica and silane coupling agent are added to the first kneaded product. When kneaded and kneaded, HTS-derived water that exists uniformly throughout the resulting kneaded product (hereinafter referred to as “second kneaded product”) promotes the reaction between the silica and the silane coupling agent. I think that. Furthermore, the hexamethylene-1,6-bis (thiosulfate) disodium salt remaining after the bound water is desorbed from the HTS is after the heating step and the vulcanizing agent are added after adding the silica and the silane coupling agent. It is considered that it is thermally decomposed in the vulcanization step to become diradical S- (CH ₂ ) ₆ -S, and acts as a crosslinking agent between rubber molecules. It is considered that the water derived from HTS hydrolyzes the alkoxysilane group of the silane coupling agent to convert it into a silanol group, and the generated silanol group reacts with silica. When water is used alone as a rubber compounding agent, there is a problem that processing problems such as rotor slip occur in the mixing process, and water is soaked into a carrier such as polar powder. And when mixed, there is a problem that it is difficult to control the raw material quality before blending due to loss due to volatilization. As in the present invention, when water is kneaded with a rubber component in the state of being bound to a specific molecule as bound water, the rubber composition can be easily compounded without causing such problems. .

According to the present invention,
a) a diene rubber;
b) silica;
c) a sulfur-containing silane coupling agent;
In the rubber composition containing the diene rubber, the diene rubber is kneaded with the silica and the sulfur-containing silane coupling agent.
d) A rubber composition characterized by being pre-kneaded with 0.1 to 10 parts by weight of HTS with respect to 100 parts by weight of the diene rubber is provided.

  In the production process of the rubber composition of the present invention, the dispersibility of silica is improved by blending silica and a silane coupling agent after kneading HTS with a diene rubber in advance, resulting in high reinforcement and resistance. It has an excellent advantage that it has wearability, which has not existed in the past.

  As the diene rubber used in the rubber composition of the present invention, natural rubber or diene synthetic rubber can be used alone or in combination of two or more thereof. Examples of the diene-based synthetic rubber that can be used in the rubber composition of the present invention include, for example, various butadiene rubbers, polyisoprene, butyl rubber, acrylonitrile-butadiene copolymer rubber, chloroprene rubber, and ethylene-propylene-diene copolymer rubber. Styrene-isoprene copolymer rubber and styrene-butadiene copolymer rubber.

The silica used in the rubber composition of the present invention can be appropriately selected from those generally used in the rubber industry, and is not limited to the production method. Examples of silica include silica produced by a wet method in which sodium silicate, sulfuric acid, and salts are reacted in an aqueous solution, and a dry method in which fine silica silicate particles are generated at a high temperature of 1000 ° C. or higher. . The silica preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 100 to 300 m ² / g. When N ₂ SA is less than 100 m ² / g, the filling amount can be increased, but the reinforcing effect is poor. Silica with N ₂ SA exceeding 300 m ² / g is difficult to disperse in the rubber component because of its high cohesiveness. In the description of the present specification, “nitrogen adsorption specific surface area (N ₂ SA)” means a specific surface area (unit m ² / g) measured according to ATSM D3037. Silica is preferably blended in an amount of 30 to 120 parts by weight with respect to 100 parts by weight of the diene rubber.

  The rubber composition of the present invention may contain a reinforcing filler other than silica, and examples of the reinforcing filler include carbon black, talc, calcium carbonate, aluminum hydroxide, magnesium carbonate and the like. Examples of carbon black that can be used in the rubber composition of the present invention include, when the rubber composition of the present invention is used as a rubber composition for a tire tread, SAF, ISAF, HAF grades are listed.

  In the rubber composition of the present invention, the sulfur-containing silane coupling agent can be appropriately selected from those generally used in the rubber industry according to the type of silica used. Specific examples of the sulfur-containing silane coupling agent that can be used in the rubber composition of the present invention include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltri Ethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthio Carbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl base Zothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide and the like can be mentioned. The sulfur-containing silane coupling agent may be used alone or in combination of two or more. It is preferable that the compounding quantity of a sulfur containing silane coupling agent is 1 to 15 weight% with respect to the total weight of the said silica. When the compounding amount of the sulfur-containing silane coupling agent is less than 1% by weight with respect to the total weight of the silica, the dispersion of the silica in the rubber component becomes poor, while when it exceeds 15% by weight with respect to the silica. , Scorch time is shortened and workability is reduced.

  HTS used in the rubber composition of the present invention forms a thermally stable cross-linked structure and is known as a heat-resistant cross-linking agent. In the production of the rubber composition of the present invention, HTS is kneaded with diene rubber in advance before kneading silica and sulfur-containing silane coupling agent with diene rubber. HTS is commercially available, for example, from FLEXSYS under the trade name DURALINK HTS. HTS is used in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the diene rubber.

  The kneading of the HTS and the diene rubber can be performed using a mixing or kneading apparatus such as a closed mixer or an open roll that is usually used for kneading the rubber composition. For example, in the case of using a closed mixer, the diene rubber is first charged into the mixer at ambient temperature, and HTS is charged simultaneously with or after the charging, and the kneading of the diene rubber and HTS is started. The temperature is raised to ˜140 ° C. and held at this temperature for 1 to 7 minutes to form a first kneaded product (hereinafter, this temperature is referred to as “first kneading temperature”). Thereafter, silica and a silane coupling agent are added to the kneaded product, and the temperature in the mixer is maintained at 130 to 150 ° C., depending on the size of the mixer and the amount of the contents of the mixer, but at this temperature range approximately 2 minutes or more. To form a second kneaded product. When the silica and silane coupling agent are added, compounding agents other than vulcanizing agents such as sulfur and vulcanization accelerators, such as carbon black, vulcanization aids, anti-aging agents, waxes, plasticizers, etc. may be added. . The second kneaded product is once discharged from the mixer, cooled, and kneaded with a vulcanizing agent such as sulfur or a vulcanization accelerator in the next mixing step.

  The rubber composition obtained by kneading HTS in advance to diene rubber, and then kneading and vulcanizing silica and sulfur-containing silane coupling agent to diene rubber containing HTS is a diene rubber containing HTS, silica and sulfur. Compared to the rubber composition obtained by adding, kneading and vulcanizing the silane coupling agent together, the HTS-derived water is almost uniform before the silica and the sulfur-containing silane coupling agent are added to the diene rubber. Since the silica is dispersed in the diene rubber, the reaction between the silica and the silane coupling agent can proceed with the silica more uniformly dispersed, and the silica remains in the dispersed state. In the subsequent vulcanization reaction, it undergoes a coupling reaction with rubber molecules, so that the dispersibility of silica in the rubber composition obtained after vulcanization is further improved, and therefore, high reinforcement and Vulcanized rubber composition having a wear resistance.

  In the rubber composition of the present invention, in addition to the above-mentioned silica, sulfur-containing silane coupling agent and HTS, various kinds of vulcanization or crosslinking agent, vulcanization or crosslinking accelerator, anti-aging agent, plasticizer, softening agent, etc. The compounding agents and additives can be compounded by a general compounding method in an amount generally used for the rubber component.

  The rubber composition of the present invention can be used in various applications where the above characteristics are required, for example, in the manufacture of tire members such as tire treads, or in the manufacture of rubber products such as hoses and belts. Since the rubber composition of the present invention has high reinforcement and wear resistance, it is particularly suitable as a tire member, and can be used as a rubber composition for tire treads that are particularly demanding for such characteristics.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but it goes without saying that the technical scope of the present invention is not limited by these examples.

Manufacture of rubber composition
Control Example For the control example, using a 3.4 liter closed Banbury mixer according to the composition of Table 1 below, rubber, silica, carbon black, sulfur-containing silane coupling agent, zinc white, etc. Were mixed for 5 minutes, discharged from a mixer at 150 ° C., and then cooled to room temperature. Thereafter, the mixture was mixed again for 5 minutes using a 3.4 liter sealed Banbury mixer, released at 150 ° C., and then mixed with a vulcanization accelerator and sulfur with an open roll to obtain a vulcanized rubber composition. .

Examples 1-6
Vulcanized rubber compositions of Examples 1 to 6 were produced in accordance with the formulation shown in Table 1 except that the amount of HTS shown in Table 2 below was previously kneaded with diene rubber. The kneading process was as follows:
The rubber and HTS are put into a 3.4 liter closed Banbury mixer, kneading is started, and after maintaining for 5 minutes at the first kneading temperature shown in Table 2, silica and a silane coupling agent are put into the mixer. The temperature was raised to 150 ° C., and kneading was performed at this temperature for 5 minutes to form a second kneaded product. When the silica and silane coupling agent were added, compounding agents other than vulcanizing agents such as sulfur and vulcanization accelerators were added. The second kneaded product was once discharged from the mixer, cooled, and kneaded with a vulcanizing agent such as sulfur or a vulcanization accelerator in the next mixing step.

Comparative Examples 1-5
Comparative Example 1 was prepared in the same manner as the Control Example except that 1 part by weight of HTS per 100 parts by weight of diene rubber was added simultaneously with the silica and sulfur-containing silane coupling agent. Comparative Example 2 was produced in the same manner as Comparative Example 1 except that HTS was added after silica and a sulfur-containing silane coupling agent were added to the diene rubber. Comparative Examples 3 and 4 were produced in the same manner as Comparative Example 1 except that the temperature at the time of mixing the diene rubber and HTS was changed. Comparative Example 5 was produced in the same manner as Comparative Example 1 except that the blending amount of HTS was changed.

Test Methods The performance of the rubber compositions obtained in the following examples and comparative examples was determined by the following test methods.
(1) Mooney coach time:
According to JIS K6300, the time for the viscosity to rise by 5 Mooney units at a temperature of 125 ° C. was measured. It was expressed as a relative value when the value for the control example was taken as 100.
(2) Pain effect:
Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., the initial strain was 10% at room temperature, and the amplitude was measured every 0.2% from 0.1 to 9.5%. The loss elastic modulus E ″ was determined, and E ′ (0) −E ″ (∞) was calculated from the Cole-Cole plot. It was expressed as a relative value when the control example was 100. The smaller the value, the better the dispersibility of the silica.
(3) Reinforcing property:
The stress at 100% elongation and 300% elongation was measured according to JIS K6251 and the ratio M300 / M100 was determined.
(4) Abrasion resistance:
Using a Lambourn Abrasion Tester (Iwamoto Seisakusho Co., Ltd.), measured under the conditions of load 5 kg, slip rate, 25%, time 4 minutes, room temperature. expressed. It shows that it is excellent in abrasion resistance, so that a numerical value is large.
The test results are shown in Table 2 below.

  From the results shown in Table 2, when HTS is added to the diene rubber before the silica and sulfur-containing silane coupling agent, HTS is added simultaneously with the silica and sulfur-containing silane coupling agent or silica and sulfur-containing silane coupling. Compared with the case where it is added after the agent, the value of the Payne effect is small and it can be seen that the silica is well dispersed. Further, when the HTS and the diene rubber are kneaded prior to the addition of the silica and the sulfur-containing silane coupling agent, when the first kneading temperature is lower than the range of 100 to 140 ° C., the value of the Payne effect becomes large. . However, when the first kneading temperature exceeds the range of 100 to 140 ° C., the Mooney scorch time is shortened, which is not preferable. It can also be seen that when the amount of HTS added exceeds 10 parts by weight with respect to 100 parts by weight of the diene rubber, the Mooney scorch time is shortened.

Claims (3)

a) a diene rubber;
b) silica;
c) a sulfur-containing silane coupling agent;
In the rubber composition containing the diene rubber, the diene rubber is kneaded with the silica and the sulfur-containing silane coupling agent.
d) 0.1 to 10 parts by weight of the following formula with respect to 100 parts by weight of the diene rubber:
NaO ₃ S—S— (CH ₂ ) ₆ —S—SO ₃ Na.2H ₂ O
A rubber composition, which is pre-kneaded with hexamethylene-1,6-bis (thiosulfate) disodium dihydrate represented by the formula below at a temperature of 100 to 140 ° C.   The amount of the silica is 30 to 120 parts by weight per 100 parts by weight of the diene rubber, and the amount of the sulfur-containing silane coupling agent is 1 to 15% by weight based on the weight of the silica. The rubber composition according to claim 1.   A pneumatic tire using the rubber composition according to claim 1 or 2 for a tire tread.